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1.
This paper compares data from linearized and nonlinear Zebiak–Cane model, as constrained by observed sea surface temperature anomaly(SSTA), in simulating central Pacific(CP) and eastern Pacific(EP) El Nio. The difference between the temperature advections(determined by subtracting those of the linearized model from those of the nonlinear model),referred to here as the nonlinearly induced temperature advection change(NTA), is analyzed. The results demonstrate that the NTA records warming in the central equatorial Pacific during CP El Nio and makes fewer contributions to the structural distinctions of the CP El Nio, whereas it records warming in the eastern equatorial Pacific during EP El Nio, and thus significantly promotes EP El Nio during El Nio–type selection. The NTA for CP and EP El Nio varies in its amplitude,and is smaller in CP El Nio than it is in EP El Nio. These results demonstrate that CP El Nio are weakly modulated by small intensities of NTA, and may be controlled by weak nonlinearity; whereas, EP El Nio are significantly enhanced by large amplitudes of NTA, and are therefore likely to be modulated by relatively strong nonlinearity. These data could explain why CP El Nio are weaker than EP El Nio. Because the NTA for CP and EP El Nio differs in spatial structures and intensities, as well as their roles within different El Nio modes, the diversity of El Nio may be closely related to changes in the nonlinear characteristics of the tropical Pacific. 相似文献
2.
Contrasting global teleconnection features of the eastern Pacific and central Pacific El Niño events
Being triggered by different physical processes, the eastern Pacific (EP) and central Pacific (CP) El Niño events have several different teleconnection features around the globe. Using the ERA-Interim re-analysis monthly data during the period 1980–2016, the El Niño-Southern Oscillation (ENSO) teleconnections on the global scale and their statistical significance are investigated, with an emphasis on the contrasting features of the EP and CP El Niño events. With some exceptions, the EP El Niño and La Niña have generally similar teleconnection patterns with the reversed sign, while in some parts of the globe different and occasionally contrasting teleconnections of the EP and CP El Niño events are identified. Compared to the CP El Niño, more regions of the world are influenced by the statistically significant positive surface pressure anomalies during the EP El Niño, particularly over the Indian Ocean, tropical Atlantic and Northern Africa. It is found that the mid-tropospheric geopotential height anomalies across the globe are significantly different during the EP and CP El Niño events. Associated with different surface pressure and mid-tropospheric geopotential height anomalies, precipitation anomalies in many regions of the world are found different during the EP and CP El Niño events, particularly over the tropical Pacific, central to eastern equatorial Atlantic and the eastern Sahara. While central and eastern equatorial Atlantic experience statistically significant negative (positive) rainfall anomalies during the EP El Niño (La Niña), the CP El Niño does not have a strong influence on the amount of annual rainfall over the equatorial Atlantic. For the first time, statistically significant anomalously dry conditions are found over some parts of the Middle East and Southwest Asia during La Niña, and over the eastern Sahara during the EP El Niño. 相似文献
3.
A meteorological reanalysis dataset and experiments of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) are used to study the boreal winter season teleconnections in the Pacific-North America region and in the stratosphere generated by Central Pacific and Eastern Pacific El Niño. In the reanalysis data, the sign of the North Pacific and stratospheric response to Central Pacific El Niño is sensitive to the composite size, the specific Central Pacific El Niño index used, and the month or seasonal average that is examined, highlighting the limitations of the short observational record. Long model integrations suggest that the response to the two types of El Niño are similar in both the extratropical troposphere and stratosphere. Namely, both Central Pacific and Eastern Pacific El Niño lead to a deepened North Pacific low and a weakened polar vortex, and the effects are stronger in late winter than in early winter. However, the long experiments do indicate some differences between the two types of El Niño events regarding the latitude of the North Pacific trough, the early winter polar stratospheric response, surface temperature and precipitation over North America, and globally averaged surface temperature. These differences are generally consistent with, though smaller than, those noted in previous studies. 相似文献
4.
The NCEP–NCAR reanalysis dataset and the Had ISST dataset(1959–2014) are used to analyze the impact of two types of El Nio events, i.e., eastern Pacific El Nio(EP-El Nio) and central Pacific El Nio(CP-El Nio) events, on the duration of major and minor sudden stratospheric warmings(SSWs) in Northern Hemisphere winter(November to February). Although the frequency of major and minor SSWs during different types of El Nio shows no distinct differences, the duration of both major and minor SSWs during CP-El Nio is shorter than that during EP-El Nio. The spatial distribution of geopotential height anomalies preceding major SSWs resembles the western Pacific(WP) teleconnection pattern, while the spatial distribution of geopotential height anomalies preceding minor SSWs bears similarity to the Pacific–North America(PNA)teleconnection pattern. An enhancement of the strength of both wavenumber 1 and wavenumber 2 is found before major SSWs. Before minor SSWs, wavenumber 1 is also strengthened, but wavenumber 2 is weakened. The analysis also reveals that EP-El Nio tends to induce positive phases of PNA and WP teleconnections, while CP-El Nio induces negative-phase WP teleconnection. As the positive phases of the PNA and WP teleconnections are related to the strengthening of wavenumber 1, EP-El Nio causes an enhancement of wavenumber 1 in the high-latitude upper troposphere and an enhancement of the upward wave flux in the high-latitude stratosphere, accompanied by a negative anomaly in Eliassen–Palm flux divergence in the subpolar stratosphere, which accounts for the longer SSW duration during EP-El Nio than during CP-El Nio. 相似文献
5.
Based on the statistical analysis the teleconnections between circulation anomalies in the atmospheric centers of action and sea surface temperature anomalies are revealed for two types of El Niño. It is demonstrated that for the Eastern Pacific El Niño stronger teleconnections are registered in the Northern Hemisphere whereas the response to the Central Pacific El Niño is much stronger in the Southern Hemisphere. The Central Pacific El Niño is characterized by the more rapid signal propagation from the tropical zone to distant regions. In some cases the pattern of interaction with the atmospheric circulation considerably differs for two types of El Niño that defines differences in the fields of weather anomalies. 相似文献
6.
7.
In this paper the Bulk Aerodynamic Formulas are used to compute the latent and sensible heat fluxes over the area 8°S-20°N, 130°-180°E for each month from January 1950 through December 1979 by using the data set of COADS supplied by N'OAA of USA. The annual and monthly geographical distributions and the seasonal cycle of heat fluxes are carried out and a seasonal change of heal tluxes for ENSO year is also obtained by compositing individual ENSO year including 1951, 1953, 1957, 1963, 1965, 1969, 1972 and 1976. It is found that outing ENSO epi sodes positive anomalies of heal fluxes appeared during the period of March to July and negative anomalies from August to March of the following year. The time series of sum of heat fluxes for March, April, May, June and July in each year from 1950 through 1979 had a significant link to the eastern tropical Pacific SST index (Wright, 1983). The correlation coefficient was 0.56. As it is found that in the latter half of each ENSO year (August-December) the frequ 相似文献
8.
The two types of El Niño that have been identified, namely the eastern Pacific (EP) and central Pacific (CP) El Niños, are known to exert different climatic impacts on the North Atlantic region during winter. Here, we investigate the characteristics of the teleconnection of the two El Niño types with a focus on the stratosphere-troposphere coupling. During the EP El Niño, polar stratospheric warming and polar vortex weakening frequently occur with a strong tendency for downward propagation near the tropopause. Consequently, the atmospheric pattern within the troposphere over the North Atlantic sector during midwinter closely resembles the negative North Atlantic Oscillation pattern. In contrast, during CP El Niño events stratospheric warming events exhibit a much weaker downward propagation tendency. This difference in the stratospheric circulation response arises from the different seasonal evolution of the tropospheric wave response to the two El Niño types. For the EP El Niño, the Aleutian Low begins growing during December and is sustained throughout the entire winter (December to February), which provides favorable conditions for the continuous downward propagation of the stratospheric warming. We also discuss the origin of the difference in the teleconnections from the two types of El Niño associated with the distinct longitudinal position of the warm SST anomaly that determines troposphere-stratosphere coupling. 相似文献
9.
10.
Joint Propagating Patterns of SST and SLP Anomalies in the North Pacific on Bidecadal and Pentadecadal Timescales 总被引：28，自引：0，他引：28
Wavelet analyses are applied to the Pacific Decadal Oscillation index and North Pacific index for the period 1900-2000, which identifies two dominant interdecadal components, the bidecadal (15-25-yr) and pentadecadal (50-70-yr) modes. Joint propagating patterns of sea surface temperature (SST) and sea level pressure (SLP) anomalies in the North Pacific for the two modes are revealed by using the techniques of multi-channel singular spectrum analysis (MSSA) and linear regression analysis with the global sea surface temperature (GISST) data and the northern hemispheric SLP data for the common period 1903-1998. Significant differences in spatio-temporal structures are found between the two modes.For the bidecadal mode, SST anomalies originating from the Gulf of Alaska appear to slowly spread southwestward, inducing a reversal of early SST anomalies in the central North Pacific. Due to further westward spreading, the SST variation of the central North Pacific leads that of the Kuroshio-Oyashio Extension (KOE) region by approximately 4 to 5 years. Concomitantly, SLP anomalies spread over most parts of the North Pacific during the mature phase and then change into an NPO(North Pacific Oscillation)-like pattern during the transition phase. For the pentadecadal mode, SST anomalies develop in the southeast tropical Pacific and propagate along the North American coast to the mid-latitudes; meanwhile,SST anomalies with the same polarity in the western tropical Pacific expand northward to Kuroshio and its extension region; both merge into the central North Pacific reversing the sign of early SST anomalies there.Accompanying SLP anomalies are characterized by an NPO-like pattern during the mature phase while they are dominant over the North Pacific during the transitional phase. The bidecadal and pentadecadal modes have different propagating Patterns, suggesting that the two interdecadal modes may arise from different physical mechanisms. 相似文献
11.
The East Asia–Pacific(EAP) teleconnection pattern is the dominant mode of circulation variability during boreal summer over the western North Pacific and East Asia, extending from the tropics to high latitudes. However, much of this pattern is absent in multi-model ensemble mean forecasts, characterized by very weak circulation anomalies in the mid and high latitudes. This study focuses on the absence of the EAP pattern in the extratropics, using state-of-the-art coupled seasonal forecast systems. The results indicate that the extratropical circulation is much less predictable, and lies in the large spread among different ensemble members, implying a large contribution from atmospheric internal variability. However,the tropical–mid-latitude teleconnections are also relatively weaker in models than observations, which also contributes to the failure of prediction of the extratropical circulation. Further results indicate that the extratropical EAP pattern varies closely with the anomalous surface temperatures in eastern Russia, which also show low predictability. This unpredictable circulation–surface temperature connection associated with the EAP pattern can also modulate the East Asian rainband. 相似文献
12.
The northwestern Pacific(NWP) is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific–Japan(PJ) teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency(SFF) index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2 M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes,indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical–subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030 s, implying a possible decline of the SFF in this period. 相似文献
13.
A Coupled General Circulation Model for the Tropical Pacific Ocean and Global Atmosphere 总被引：3，自引：0，他引：3
On the basis of Zeng’s theoretical design, a coupled general circulation model (CGCM) is developed with its characteristics different from other CGCMs such as the unified vertical coordinates and subtraction of the standard stratification for both atmosphere and ocean, available energy consideration, and so on. The oceanic component is a free surface tropical Pacific Ocean GCM between 30oN and 30oS with horizontal grid spacing of 1o in latitude and 2o in longitude, and with 14 vertical layers. The atmospheric component it a global GCM with low-resolution of 4o in latitude and 5o in longitude, and two layers or equal man in the vertical between the surface and 200 hPa. The atmospheric GCM includes comprehensive physical processes. The coupled model is subjected to seasonally-varying cycle. Several coupling experiments, ranging from straight forward coupling without flux correction to one with flux correction, and to so-called predictor-corrector monthly coupling (PCMC), are conducted to show the existence and final controlling of the climate drift in the coupled system. After removing the climate drift with the PCMC scheme, the coupled model is integrated for more than twenty years. The results show reasonable simulations of the annual mean and its seasonal cycle of the atmospheric and oceanic circulation. The model also produces the coherent interannual variations of the climate system, manifesting the observed El Ni?o / Southern Oscillation (ENSO). 相似文献
14.
R. M. Roman-Cuesta L. Rejalaga-Noguera C. Pinto-García J. Retana 《Climatic change》2014,127(2):243-256
Bolivia is located at the crossroad of the major climatic influences of Northern and Southern-South America, which turns this country into a natural laboratory to investigate the interactions between ocean-climate and fire variability. We chose two oceanic indices: MEI (multivariate ENSO Index) and AMO (Atlantic Multidecadal Oscillation) to select the three most representative years for four oceanic conditions: El Niño, La Niña, AMO, and standard years (understood as years with little ocean influences), for the period 1992–2012. We investigated how i) rainfall (dry vs wet seasons) and ii) fire responded in five Bolivian biomes (Tropical Moist Forests, Tropical Dry Forests, Tropical Grasslands, Tropical Montane, and Seasonally Flooded ecosystems) under these oceanic conditions. Bolivia showed a strong rainfall increase in El Niño years in both seasons (wet/dry), while AMO showed the strongest droughts in both seasons. La Niña showed a bipolar response with rainfall increases in the wet season and a very marked rainfall decrease in the dry season. Drought significantly increased fire numbers in AMO years, being the most significant fire condition and suggesting a larger fire influence of the Atlantic than the Pacific at the national level. Surprisingly, the amount of fire was very large under normal years (STD) and similar to fire levels under La Niña, suggesting generalized fire conditions in the country, except for El Niño years that bring rainfall excess and little fire. The most fire-affected biomes were the seasonally flooded and dry forests, followed by the grassland/savannah biome. Montane areas showed the least fire, but satellite fire omission is well known in the Andean region. 相似文献
15.
Hai ZHI Zihui YANG Rong-Hua ZHANG Pengfei LIN Jifeng QI Yu HUANG Meng DONG 《大气科学进展》2023,(7):1269-1284
It has been recognized that salinity variability in the tropical Pacific is closely related to the Interdecadal Pacific Oscillation(IPO). Here, we use model simulations from 1900 to 2017 to illustrate obvious asymmetries of salinity variability in the tropical Pacific during positive and negative IPO phases. The amplitude of salinity variability in the tropical Pacific during positive IPO phases is larger than that during negative IPO phases, with a more westward shift of a large Sea Surface Sal... 相似文献
16.
One of the fundamental questions concerning the nature and prediction of the oceanic states in the equatorial eastern Pacific is how the turnabout from a cold water state (La Ni?na) to a warm water state (El Ni?no) takes place, and vice versa. Recent studies show that this turnabout is directly linked to the interannual thermocline variations in the tropical Pacific Ocean basin. An index, as an indicator and precursor to describe interannual thermocline variations and the turnabout of oceanic states in our previous paper (Qian and Hu, 2005), is also used in this study. The index, which shows the maximum subsurface temperature anomaly (MSTA), is derived from the monthly 21-year (1980–2000) expendable XBT dataset in the present study. Results show that the MSTA can be used as a precursor for the occurrences of El Ni?no (or La Ni?na) events. The subsequent analyses of the MSTA propagations in the tropical Pacific suggest a one-year potential predictability for El Ni?no and La Ni?na events by identifying ocean temperature anomalies in the thermocline of the western Pacific Ocean. It also suggests that a closed route cycle with the strongest signal propagation is identified only in the tropical North Pacific Ocean. A positive (or negative) MSTA signal may travel from the western equatorial Pacific to the eastern equatorial Pacific with the strongest signal along the equator. This signal turns northward along the tropical eastern boundary of the basin and then moves westward along the north side of off-equator around 16N. Finally, the signal returns toward the equator along the western boundary of the basin. The turnabout time from an El Ni?no event to a La Ni?na event in the eastern equatorial Pacific depends critically on the speed of the signal traveling along the closed route, and it usually needs about 4 years. This finding may help to predict the occurrence of the El Ni?no or La Ni?na event at least one year in advance. 相似文献
17.
The ENSO Events in the Tropical Pacific and Dipole Events in the Indian Ocean 总被引：1，自引：0，他引：1 
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下载免费PDF全文 A depth map (close to that of the thermocline as defined by 20℃) of climatically maximum seatemperature anomaly was created at the subsurface of the tropical Pacific and Indian Ocean, based on which the evolving sea-temperature anomaly at this depth map from 1960 to 2000 was statistically analyzed. It is noted that the evolving sea temperature anomaly at this depth map can be better analyzed than the evolving sea surface one. For example, during the ENSO event in the tropical Pacific, the seatemperature anomaly signals travel counter-clockwise within the range of 10°S-10°N, and while moving, the signals change in intensity or even type. If Dipole is used in the tropical Indian Ocean for analyzing the depth map of maximum sea-temperature anomaly, the sea-temperature anomalies of the eastern and western Indian Oceans would be negatively correlated in statistical sense (Dipole in real physical sense), which is unlike the sea surface temperature anomaly based analysis which demonstrates that the inter-annual positive and negative changes only occur on the gradients of the western and eastern temperature anomalies. Further analysis shows that the development of ENSO and Dipole has a time lag features statistically, with the sea-temperature anomaly in the eastern equatorial Pacific changing earlier (by three months or so). And the linkage between these two changes is a pair of coupled evolving Walker circulations that move reversely in the equatorial Pacific and Indian Oceans. 相似文献
18.
In the past three decades, the strongest central Pacific (CP) El Niño event was observed in 2009–2010 by satellites. When intensity of this CP El Niño reached its maximum, large diurnal variations of sea surface temperature (SST) were also observed from tropical atmosphere ocean moorings in the central equatorial Pacific. Solar radiation in the equatorial central Pacific is larger than 140 W/m2, which leads to the amplitude of diurnal cycle of SST primarily determined by large-scale wind patterns. Intraseasonal westerly wind events (WWEs) can lead to an eastward displacement of the warm pool and also can weaken the trade winds in central Pacific. When the occurrence of equatorial WWEs is more than 20 days in a month, monthly mean wind speed in central equatorial Pacific has high possibility of wind speed less than 3 m/s, thus has pronounced diurnal cycle of SST. The diurnal cycle of SST will rectify daily mean SST. Reduced mixing at the base of the mixed layer and suppression of entrainment due to the accumulated effect of diurnal cycle may lead to warmer SST in the following month. This study suggests the occurrence of more diurnal SST events may contribute to the increasing intensity of the CP El Niño events. 相似文献
19.
Propagation of Strong Wave Package Center and Latitudinal Movement of Western Pacific Subtropical High 下载免费PDF全文
下载免费PDF全文 On the basis of studying wave package propagation,this paper investigated the relationship between high frequency wave package propagation and transient waves' evolvement or the subtropical high's latitudinal movement.The results showed that during winter the lifetime of wave package was longer and usually persisted for 7-10 days with a propagating speed of 2-10 m s~(-1).Usually they propagated southeastward at the beginning,then turned to northeast.During summer the lifetime and intensity of wave package became shorter and weaker.It availed development (attenuation) of troughs when the strong wave package center was intensified (weakened) which overlapped with trough.If strong wave package center kept overlapping with ridge,the ridge would abate later in a few days.Obvious jumping northward (retreating southward) processes of Western Pacific subtropical high (WPSH) were (not) usually related to strong wave package centers located at South China Sea area (South Asia area and Temperate Zone) for 5 days or longer.After two seasonal jumping processes,there were persisting strong wave package centers for 5 days or longer. WPSH retreating processes were also related to activities of strong wave package centers over South Asian area and temperate area as well as the strong wave package centers of typhoon,and all these centers persisted for 5 days or longer. 相似文献
20.
This study reveals the strengthened interdecadal relationship between the western North Pacific summer monsoon(WNPSM) and tropical central-western Pacific sea surface temperature anomaly(SSTA) in summer after the early 1990s.In the first period(1979–91, P1), the WNPSM-related precipitation anomaly and horizontal wind anomaly present themselves as an analogous Pacific-Japan(PJ)-like pattern, generally considered to be related to the Ni?o-3 index in the preceding winter. During the subsequent peri... 相似文献